A recent move by Beijing to block access to several VPN services has angered some Chinese free speech activists who use the tools to get around China’s formidable Internet firewalls.

But now some analysts worry the move may signal a much larger and longer-lasting crackdown that could seriously cramp the Communist nation’s struggling economy.

Users in China of several VPN services, among them VyprVPN, Astrill and StrongVPN, began reporting they were being blocked from accessing those services on the Internet.

VPN’s, or "virtual private networks," are used to bypass Internet censorship and filtering. In recent years, VPNs have proven very popular in China, not just among free speech activists but with many firms conducting international business from China.

In a Twitter message to its users, Astrill confirmed the blocks, but said only iOS devices, such as iPads and iPhones, appeared to be targeted.

Analyzing Web traffic

Over at its company blog, Golden Frog, the firm behind VyprVPN, also confirmed the new blocks, saying that it "appears that China is using Deep Packet Inspection (DPI) to analyze plain-text Web traffic through the Great Firewall."

In response, the company is now using the encrypted HTTPS protocol to help bypass China’s DPI filters.

"The authorities have been doing this for a long time," writes the pseudonymous "Charlie Smith" of the GreatFire.org censorship monitoring site in an email to VOA. "But they have never done it as extensively as they are doing it now."

Smith said his group has been monitoring a "rapid ramping up of Internet controls" in China since June of 2014, and that blocking VPNs -- which the government has mostly ignored up to this point -- is just the next logical step to tighten control.

"Google got blocked completely last June for the first time. Gmail got blocked completely for the first time in December," he wrote. "Since October, the authorities have launched attacks on Yahoo, Google, Microsoft and Apple, putting sensitive user information at risk and in turn making Chinese netizens suspicious of using foreign services.

"All of that activity drives Internet users to adopt circumvention tools," he wrote. "By blocking these tools, the authorities are leaving people no option but to use domestic services."

Services, he adds, that can easily be monitored, filtered or cut off entirely.

In a written statement to VOA, the U.S. State Department urged authorities in Beijing to lift the blocks and open up a freer Internet.

"We remain deeply concerned by Chinese government efforts to restrict the free flow of information both offline and online, including the continued blocking of foreign media websites and search engines," the statement said. "Such actions run counter to China’s international commitments to protect freedom of expression."

However, the South China Morning Post reports that at a Beijing news conference on January 27, Wen Ku, communication development director at the Ministry of Industry and Information Technology, said that new technologies, such as VPNs, make it entirely appropriate for the government to take whatever steps deemed necessary to filter out "inappropriate information" from reaching those online in China.

China’s next moves

There are hundreds of VPN services, but overall they all work the same way. A VPN creates what’s commonly called a "tunnel" -- a point-to-point, encrypted connection between your computer and a particular set of servers associated with that VPN service. This tunnel allows users to generally access the sites they wish while hiding their location and identity.

VPNs are effective but not foolproof, and generally can be blocked in two ways.

First, governments can block access to the servers associated with a VPN, which is why some VPNs use a constantly shifting set of servers across different continents.

Second, as happened at Golden Frog, the websites of VPN companies can simply be blocked, preventing users from ever downloading a service in the first place.

Internet censorship in China is nothing new, dating back as far as 1998 and the introduction of what’s often termed "The Great Firewall of China."

What’s of concern to some analysts now is not only that VPNs are being targeted, but more and more websites are being blocked long-term.

"The government in China has consistently attempted to monitor the Internet and restrict social media in China, which is growing by leaps and bounds," said Michael Auslin, scholar in residence at the American Enterprise Institute, where he focuses on Asian politics and security.

"This is a particularly sensitive time for the government, one in which the consolidation of power by Xi Jinping is taking on some very sensitive sacred cows, at low and high levels," Auslin said.

"This is not a time when the government wants to lose control of the national debate. They long ago learned the lesson of the Soviet Union. China wants to maintain political and social control and allow economic reform. That’s the opposite of what the Soviets did and, of course, they collapsed," he added.

Internet and social media use in China is exploding; the micro-blogging site Sina Weibo alone has over 500 million users.

Around the firewall

As authorities have broadened the number of sites being blocked, Chinese netizens have found new ways around the firewall, including using cloud services like Amazon S3, which have become critical for many Chinese businesses to make money.

Blocking those services, said GreatFire's "Smith," creates economic "collateral damage" for Chinese business, which in turn increases pressure on China’s leaders to loosen their grip on the Web.

A few analysts have begun raising the possibility that China may eventually follow Iran’s lead and try to build its own intranet, walling off nearly the entire global Internet to all but a select few in that nation.

"One of the biggest problems is it would be disruptive, and that’s not something the government right now wants," he said. "There’s already an economic slowdown, so the government clearly does not want any economic uncertainty or instability."

That said, Auslin agrees with "Smith" and others that this most recent action blocking VPNs further reinforces China’s apparent desire to seize as much control of the Internet as possible, and that officials may be seriously considering creating a de facto intranet through heavy filtering and censorship.

“There certainly is the potential that if they felt they could get away with it, and they felt it would not harm business, they would probably go ahead and do it,” he said.

You can learn much more about VPNs, Web censorship and how to get around firewalls at VOA’s new on-going project “Circumventing Censorship”, a digital handbook to help you get where you want to go online and protect your privacy.

Doug Bernard covers cyber-issues for VOA, focusing on Internet privacy, security and censorship circumvention. Previously he edited VOA’s “Digital Frontiers” blog, produced the “Daily Download” webcast and hosted “Talk to America”, for which he won the International Presenter of the Year award from the Association for International Broadcasting. He began his career at Michigan Public Radio, and has contributed to "The New York Times," the "Christian Science Monitor," SPIN and NPR, among others. You can follow him @dfrontiers.